The present invention relates to masers and more particularly to an improved getter for a hydrogen maser.
Apparatus of the maser type have been steadily improved since their inception in 1954 and now perform a variety of tasks in many diverse fields. Masers are frequently employed as very low noise amplifiers, are useful in some military radar applications, and are most useful in radio astronomy. At microwave frequencies, masers have been used as generators of radiation for clocks or frequency standards.
In U.S. Pat. No. 2,972,697, entitled, "Molecular Beam Apparatus Of The Maser Type", which issued Feb. 21, 1961, to Stanley A. Johnson and Ferris Eugene Alger, there is described the use of a getter for removing extraneous gases in a vacuum chamber. In this patented device, a getter chamber is connected with a vacuum chamber and the getter chamber contains a heater filament for evaporating a getter material, such as titanium, from a crucible. The titanium is deposited upon the inner walls of the getter chamber as a metallic film and serves as a getter for removing extraneous gases which may be present in the vacuum chamber. The filament is only heated at intervals for the purpose of renewing the getter film.
In a commercially available getter cartridge, a zirconium-aluminum alloy is sintered onto strips of iron and the active material is the zirconium-aluminum alloy. This getter, however, has the disadvantage in that the zirconium-aluminum alloy flakes off the iron substrate after absorbing about 20 Torr-liters/gm because the alloy becomes embrittled, swells and cracks upon absorbing hydrogen. These flakes continue to pump, that is, their equilibrium hydrogen pressure is still well below the 10.sup.-6 Torr pressure desired by the maser even after 20 Torr-liters/gm absorption, however, in a zero-g environment, these flakes drift around the pump, drift out the port and generally annoy the maser with their presence.